1. Field of the Invention
The present invention is concerned with UV ray irradiation equipment used for UV ray irradiation of untreated water for sterilization, oxidative decomposition of organics, decomposition of harmful substances, etc.
2. Description of the Prior Art And Related Information
When the conventional UV irradiation equipment has been used for an extended period of time for the purpose of removing impurities from untreated water such as sewage, iron, hardness components such as calcium and so forth precipitate on the surface of the UV ray transmission tubes which have internal UV ray irradiation lamps therein which surface comes in contact with the untreated water. These precipitates (or scale) obstruct the transmission of UV rays through the UV ray transmission tubes and deteriorate the irradiation efficiency and therefore degrade the purity of the treated water. To cope with the above-mentioned deterioration of UV ray transmission efficiency due to fouling on the surface of the UV ray transmission tubes, scrapers made of rubber, Teflon.RTM. and the like have been used to physically clean the surface of the UV ray transmission tubes. However, this physical method of scraping the surface of the UV ray transmission tubes leaves much to be desired as hardness components and other scales deposited on the surface of the UV ray transmission tubes usually consist of very fine particles which tend to penetrate into and clog concave pits on the surface, thereby making it difficult to wash out such scale by scrapers.
Alternatively, the UV ray transmission tubes are immersed in a tank filled with a cleaning solution such as a solution of weak acids, e.g. phosphoric acid, a solution of scale dispersant or the like, thereby removing scale such as hardness components from the surface of the UV ray transmission tubes.
The foregoing chemical cleaning of the surface of the UV ray transmission tubes has the following drawbacks:
(1) It is cumbersome and time-consuming to disassemble a UV ray transmission tube on the surface of which scale such as hardness components has deposited and to immerse the tube in a cleaning tank. PA1 (2) In order to carry out the above-mentioned cleaning work, ongoing UV irradiation has to be suspended, which in turn results in deterioration of the UV irradiation efficiency. PA1 (3) An excessive quantity of cleaning solution has to be used in the cleaning tank, which entails an expensive cleaning cost. PA1 (4) The cleaning work is not amenable to automation and cannot therefore go with the trend of equipment automation. PA1 (1) To easily clean off in situ scale comprised of hardness components, etc. from a UV ray transmission tube without disassembling the UV ray irradiation unit and taking out the tube(s) fouled with scale; PA1 (2) To keep up the UV irradiation efficiency without interrupting the UV irradiation process for cleaning work to remove scale comprised of hardness components, etc. and deposited on the UV transmission tube; PA1 (3) To minimize the cleaning cost by reducing the consumption of cleaning solution by feeding a small quantity of a cleaning solution to the surface of the UV ray transmission tube and cleaning off scale comprised of hardness components, etc. and deposited on the surface of the UV ray transmission tube by means of a scraper ring; and PA1 (4) To facilitate automation of the cleaning work thereby going with the trend of equipment automation.
Accordingly, a need presently exists for a means of more efficiently and economically cleaning scale from the surfaces of UV ray transmission tubes used in UV ray treatment systems.